Conducting or electroactive polymers have attracted significant attention in recent decades because of their potential applications in various fields such as light weight batteries, electochromic displays, electroluminescent devices and in sensors. Among the conducting polymers, polyaniline is unique because of its high electrical conductivity, good environmental stability and easy preparation.
C-MET developed Polyaniline and its substituted dertivatives as Humidity sensors (humidity ranging between 20-100 % RH). The polymers were synthesized by chemical polymerization method using ammonium peroxydisulphate as an oxidizing agent at 0-5 0C. A variety of acids (viz. Organic, Inorganic Sulphonic and Polymeric acids) were used for the doping of the polymers. Synthesized polymers were characterized by various analytical techniqes, e.g. UV-Vis. and FT-IR spectroscopy, SEM analysis, conductivity measurements, TG/SDTA and DSC analysis.
Polyaniline, poly(o-toluidine), poly(o-anisidine) and Poly(N-methyl aniline) doped with different acids were then tested as materials for humidity sensor. The humidity sensing measurements were performed by using static as well as dynamic humidity measurement systems.
Among the different polymers synthesized and utilized as sensor, Polyaniline doped with p-Toluene sulphonic acid shows linear response in the range of 20-80 % RH, While Poly(o-Anisidine) doped with Camphor sulphonic acid shows the best sensing response in the range of 20-100 % RH. Also,
Poly(N-methyl aniline) doped with Phosphoric acid showed the best sensing response for a broad range of humidity (20-100 % RH) and was found to be the best candidate for a humidity sensor.
Thin, free standing as well as substrate adhered films of the Polyaniline were also prepared by using appropriate solvents and tested for humidity sensing measurements. Trials were also performed for the preparation of the Interdigitated Pattern of copper electrode on the glass and alumina substrates by Photolithographic techniques.
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